This invention relates to an ultrasonic pump for pumping a non-solid medium or fluid, such as a liquid, a liquid metal, a gas or an aerosol, via absorption by the medium of non-planar focused ultrasonic longitudinal waves directly generated by a single- or broad-bandwidth, non-planar transducer.
There are many types of electromechanical pumps utilized today to pump fluids, such as gear pumps, centrifugal pumps, roller pumps, piston and peristaltic pumps, all of which require moving parts for proper operation. Typically, these moving parts are designed in relation to the amount of fluid to be pumped per unit time and the overall volume of the physical pump design.
Piston pumps are generally defined as having rotating pistons of varying stroke lengths to pump fluid media through check valves. Because piston pumps are capable of generating great pressure, they are suitable for high pressure applications. Nevertheless, piston pumps require many moving parts such as a piston, piston rod, crankshaft, and associated valve assemblies.
Peristaltic pumps are generally defined as having rollers driven by a motor which push a fluid medium along the internal diameter of tubing as the rollers are rotated by the motor. Peristaltic pumps are considered safe, mainly because the pumped the fluid medium never contacts an environment different than the surfaces of the internal tubing. They are used widely in the medical and pharmaceutical sector where the prevention of contamination is a factor. One major disadvantage associated with peristaltic pumps lies in the possible crushing forces that result upon the fluid medium being pumped, in those instances where the tubing constricts completely. Moreover, the moving parts of the peristaltic pumps usually undergo fatigue, as a result of their continuous operation and this can result in particles being shed from the tubing.
There are also for consideration the operation of sonic and ultrasonic pumps that feature as an embodiment the use of acoustic waves for their principle of operation, for example,. Mandroian U.S. Pat. No. 3,743,446, Lucas U.S. Pat. No. 5,020,977, and Lucas U.S. Pat. No. 5,263,341, Haller et al., U.S. Pat. No. 6,010,316, Culp, U.S. Pat. No. 5,267,836, Oeftering, U.S. Pat. No. 6,029,518, Oeftering, U.S. Pat. No. 5,520,715, Oeftering, U.S. Pat. No. 6,003,388, Murphy, U.S. Pat. No. 4,753,579, Murphy, U.S. Pat. No. 4,684,328, Kamen et al., U.S. Pat. No. 5,349,852, Meise, U.S. Pat. No. 5,295,791, White, et al., U.S. Pat. No. 5,212,988, Keilman, U.S. Pat. No. 4,475,376, Haller and Khuri-Yakub, U.S. Pat. No. 6,010,316, Masahiro, JP 550005454A2, Kazuo, et al., JP 62191679A2, and Kawai, et al., JP 5079459A2.
Referring to U.S. Pat. No. 3,743,446, invented by Mandroian, it uses a source of sound from a fluctuating diaphragm or piezoelectric transducer that oscillates at a preselected frequency. The frequency of oscillation of the diaphragm piezoelectric transducer and the length of the pump chamber are configured together so that this arrangement forms a resonant cavity (chamber) where acoustic standing waves are established in the fluid which allows for a pressure node or antinode at the wall opposite the diaphragm piezoelectric transducer.
Referring now to U.S. Pat. Nos. 5,020,947 and 5,263,341, each invented by Lucas, the theory of operation and so with the basic embodiment of both patents acknowledges the objective of using standing waves of acoustic pressure for creating nodes which are periodic points of minimum pressure and antinodes which are periodic points of maximum pressure. These nodes and antinodes are required to be precisely located at the entrance and exit fluid ports and, thus, the standing wave phenomenon as relied upon in Lucas requires a resonant state for proper operation. Moreover, the compressors in the Lucas patents require that a very narrow resonant operational frequency range be utilized by way of special electronic control circuitry, which includes a microprocessor controlled phase locked loops to insure frequency stability, thus adding to the complexity of the design. Such control circuitry is necessary for such a complex compressor system used for refrigeration.
Thus, the essence of the compressors described in the Lucas"" patents require the creation of a standing wave within a resonant chamber or cavity and attempts to maintain the standing wave with its fixed periodic nodes and antinodes of pressure.
Turning now to U.S. Pat. No. 5,349,852, invented by Kamen et al., it describes a method of controlling a pump by using an acoustically resonant chamber driven by a loudspeaker to measure the volume of fluid in the chamber. There is no acoustic aspect to the pumping action and, in fact, this method of pump control could be applied to virtually any type of pump.
U.S. Pat. No. 5,378,120, invented by Taig, concerns a piezoelectric pump, not an ultrasonic pump. A stack of piezoceramic material is driven with a voltage to produce a volume displacement of fluid in a chamber. The piezoelectric stack is driven at a low (probably sonic) frequency to resonate a diaphragm which also acts as a check valve for the pump. This pump does not produce or rely upon ultrasonic waves or momentum transfer from the waves to the fluid.
U.S. Pat. No. 5,295,791, invented by Meise, concerns a low-frequency device wherein an acoustic resonance is established in a gas within a tube. Pressure differences at nodes and anti-nodes are used to advantage for refrigeration because there is a temperature differential between the two. This type of device has much in common with an organ pipe or a musical instrument, where a resonant tube is used to produce sound, except here they are using the structure in reverse: sound is applied, and a temperature difference results.
U.S. Pat. No. 5,212,988, invented by White, et al., describes the basic principles of a SAW sensor. These devices operate typically at several hundred MHz. A Lamb wave (a type of surface wave) is generated on the surface of a plate. The plate is coated with a polymer that is sensitive to the desired substance; usually, it absorbs the material, and changes its mass. The Lamb wave velocity and attenuation are affected by the changing properties of the polymer xe2x80x9csensorxe2x80x9d film, and so you measure the Lamb wave and infer what is being sensed by the film.
Japanese Patent Document No. 62191679A2, authored by Kazuo, et al., concerns a xe2x80x9cresilientxe2x80x9d plate, such as possibly rubber, attached to a tapered end of a horn-type transducer. These devices typically operate in the range of 10 to 30 kHz. Basically, this is a diaphragm-type pump, where the diaphragm is being driven by an ultrasonic horn transducer. Nevertheless, the pumping action is mechanical and is unrelated to any acoustic waves that it might also produce in the fluid.
Japanese Patent Document No. 5079459A2, authored by Kawai, et al., appears to describe an ultrasonic motor which is being used to drive a micropump. The motor seems to function by producing a vibration in a plate which travels in a circle and causes a rotating element to turn in one direction, and are quite common in many items such as camera lenses. This is a low-frequency (audio range) device.
U.S. Pat. No. 4,475,376, invented by Keilman, describes an ultrasound transducer testing device. It has a focused ultrasonic transducer at the large end of a fluid-filled conical chamber, which tapers down to a small opening at the other end.
U.S. Pat. No. 6,010,316, invented by Haller and Khuri-Yakub, concerns an ultrasonic micro pump which describes a planar transducer and requires a simple high-velocity plano-concave lens to focus the ultrasonic waves generated by a transducer. The lens described by Haller et al is limited because of its material properties (silicon nitride, density 3.27 g/cm3, longitudinal sound velocity of about 11,000 m/sec and an impedance of 36.0 Mrayls). Apparently, this material was used because it is easily achieved on a silicon wafer. It is, however, an extremely poor choice acoustically because of the high degree of acoustic mismatch between silicon nitride and water (36 vs. 1.485 MRayls). It is believed that this will result in approximately 15% power transmission from the lens into the water at normal incidence, and even less than about 15% transmitted at oblique incidence (i.e., near the periphery of the lens). The xcx9c85% of the power that reflects back into the lens will be partially converted into a shear wave and part will remain as a longitudinal wave traveling within the silicon nitride. These waves will reverberate within the silicon nitride. While perhaps a small fraction of the energy will ultimately reflect in such a manner as to couple into the water, but even if it does so, it will likely be out of phase with the directly-coupled water signal, and thus it will distort the beam focus. This lens will likely only effectively couple 15 percent of the power into the water.
Alternatively, Hailer et al. describes an interdigital transducer which generates surface waves that are then mode converted to pump medium or fluid. In addition, this Hailer et al patent refers to a xe2x80x9cpumping channelxe2x80x9d that is 6.25 xcexcm2 to 2.25 mm2 in cross-sectional area (Note: 1 xcexcm =1 micron=0.001 mm) and it states that the ultrasonic frequency is 1 GHz to 1 MHz. It appears from column 3, lines 30-33, that the channel is preferably sized for single-mode propagation, which means that the channel is basically one acoustic wavelength wide and one wavelength high and square in cross-section. This patent further states that at 1 MHz, it should be 1.5 mm wide (which corresponds to the 2.25 mm2 cross-sectional area in claim 1), at 600 MHz it should be 2.5 xcexcm wide (corresponding to 6.25 xcexcm2 in claim 1), and at 1 GHz it should be 1.5 xcexcm wide (or 2.25 xcexcm2).
The present invention overcomes and alleviates the above-mentioned drawbacks and disadvantages in the art through the discovery of an ultrasonic pump that utilizes acoustic streaming to ultrasonically pump a medium.
Generally speaking, an ultrasonic pump of the present invention comprises a single bandwidth or broad bandwidth, non-planar transducer which radiates non-planar focused ultrasonic waves and a chamber having a large opening at the first end for receiving the medium to be pumped and a smaller opening or exit orifice at the second end for expelling the pumped from the chamber. More specifically speaking, an ultrasonic pump of the present invention not only includes a single-bandwidth or broad-bandwidth, non-planar transducer which radiates non-planar focused ultrasonic waves and a chamber for receiving therein a medium to be pumped, it further includes a housing having an entry orifice in communication with the chamber for directing the medium from outside of the housing or pump into the chamber and an outlet for communicating with the smaller opening or exit orifice at the second end of the chamber for permitting the medium to exit the chamber and housing or pump. In addition, the chamber may include a nozzle strategically positioned adjacent the smaller opening or exit orifice at the second end of the chamber at approximately the focal zone of the non-planar, focused ultrasonic longitudinal waves for further imparting momentum to the medium being pumped, so as to enhance the expulsion of the medium through the chamber and the outlet. While the chamber may be of any shape or size, so long as the chamber shape and size does not interfere with the non-planar, focused longitudinal ultrasonic waves generated by the non-planar transducer, the chamber shape and size is preferably conical or tapered and corresponds to the beam pattern of the non-planar, focused ultrasonic longitudinal waves directly generated in the medium by the non-planar transducer.
In accordance with a further feature of the present invention, the non-planar transducer is disposed at the first end of the chamber and directly produces a non-planar, focused energy wave within the medium to which momentum is imparted for pumping the medium through the chamber and then out of the exit orifice at the second end of the chamber and the outlet of the housing. In other words, the ultrasonic pump functions by directly generating non-planar, focused ultrasonic energy (ultrasonic longitudinal or traveling waves) in the medium which is absorbed by the medium for imparting momentum to the medium. Thus, momentum from the non-planar, focused ultrasonic waves is transferred to the medium as the waves are absorbed. This phenomenon is known as acoustic streaming.
In yet another feature of the present invention, a nozzle is formed with a material, such as metal, silicon, glass, etc., which conducts heat from the medium to be pumped and preferably has a melting point higher than the boiling point of such medium. Thus, as contemplated by the present invention, the nozzle will act as a heat sink to dissipate the heat generated in the pumped medium, so as to prevent the nozzle region from becoming too hot and/or melting.
In still a further feature of the present invention, the pumped medium preferably exits the exit orifice at the second end of the chamber and the outlet of the housing in the same plane, without angle as to the exit orifice and outlet, to maximize medium flow. In addition, tubing connected to the outlet of the housing is preferably made of a material, such as plastic, which has the ability to absorb and dissipate the ultrasonic longitudinal waves, so that undesired wave reflection back into the chamber following medium expulsion is minimized or prevented.
It should therefore now be apparent to those versed in this art that a general object of this invention is to provide an ultrasonic pump in which medium is caused to flow in through a flow-channel or chamber by the interaction between non-planar, focused longitudinal acoustic waves and the medium to be pumped.
It should also be apparent that another object of the invention is to provide an ultrasonic pump which has no moving parts and can easily be fabricated by machining techniques.
It is yet another object of the invention to provide an ultrasonic pump which can be integrated with control electronics.
It is another object of the invention to provide an ultrasonic pump which can be fabricated from materials which do not react with the medium being pumped.
It is still another object of the invention to provide an ultrasonic pump in which the medium flow can be electronically controlled.
Further additional objects and advantages of the invention provide an ultrasonic pump:
(1) with no moving parts which makes use of momentum transfer from acoustic waves generated from a non-planar transducer which exerts radiation force upon the medium,
(2) which is equipped with a single bandwidth or broad bandwidth, non-planar transducer, preferably, but not necessarily, spherical in shape, for directly generating non-planar, focused, longitudinal traveling waves in the medium,
(3) having a chamber, preferably conical or tapered in shape, which corresponds to the conical or tapered pattern of the non-planar, focused ultrasonic longitudinal traveling waves generated by the non-planar transducer for directing the medium to be pumped,
(4) having a chamber which includes openings at opposite ends thereof wherein there is an inlet at one end for receiving the medium to be pumped through the chamber and an outlet at the other end for expelling the medium that has been pumped through the chamber,
(5) having a chamber wherein the inlet is located approximately near or adjacent the non-planar transducer and directs the medium to be pumped into the chamber at the same or different angles in which the non-planar, focused ultrasonic longitudinal traveling waves generated by the non-planar transducer travel,
(6) having a chamber whose open end adjacent the inlet is preferably of the same or similar shape and size as the non-planar transducer,
(7) having a nozzle, preferably conical or tapered in shape, which is positioned adjacent or near the outlet and selectively and strategically located at approximately the focal zone of the non-planar, focused ultrasonic longitudinal traveling waves generated by the non-planar transducer for imparting additional momentum to the medium being pumped,
(8) having a nozzle preferably made of a material which has a melting point greater than the boiling point of the medium to be pumped and which acts as a heat sink for conducting or absorbing heat from the pumped medium,
(9) in which the medium to be pumped exits the pump in the same plane and at the same angle as the exit opening of the nozzle or chamber,
(10) having a hollow tubing connected to the pump for receiving the pumped medium exiting the pump, which is preferably made of a material which can absorb the non-planar, focused ultrasonic longitudinal traveling waves generated by the transducer from the exiting medium, so as to minimize or avoid unwanted reflection of the ultrasonic longitudinal traveling waves generated by the transducer back toward the chamber,
(11) having an arrangement of transducers using either single-bandwidth frequency range or broad-bandwidth frequency range transducers,
(12) to provide pumping action not requiring a resonant pump chamber, thereby eliminating numerous special arrangements inherent with such resonant pump designs,
(13) to provide an ultrasonic pump with complete isolation of the medium from the outside environment, to provide a pump with one chamber and with one transducer,
(14) to provide an ultrasonic pump with various frequency selections from a broad-band ultrasonic transducer to accommodate various media to be pumped,
(15) to provide an ultrasonic pump usable at high frequencies, e.g. 1 MHZ or more,
(16) to provide an ultrasonic pump without requiring a resonant mode for operation thus eliminating complex control circuitry for basic operation,
(17) to provide an ultrasonic pump either without or in combination with a lens to focus the ultrasonic waves generated by the transducer,
(18) to provide an ultrasonic pump which does not generate surface waves that are then mode converted to pump medium or fluid, and
(19) to provide a method of creating a focused zone within the pump for establishing greater energy densities within the medium for imparting larger values of momentum to the medium thus enhancing pumping action, and thereby providing with this focused surface waves that are then mode converted to pump medium or fluid, and
(19) to provide a method of creating a focused zone within the pump for establishing greater energy densities within the medium for imparting larger values of momentum to the medium thus enhancing pumping action, and thereby providing with this focused zone a well defined volume of the medium which will produce cavitation.
The foregoing and other objects of the invention are achieved by, for example, an ultrasonic pump which includes a conically-shaped or tapered chamber for directing the medium, without interfering with the non-planar, focused longitudinal acoustic waves generated directly by the non-planar transducer, to cause the medium to flow along the conical or tapered chamber in the direction of the longitudinal acoustic waves.
These and other objects, features, and advantages of the present invention may be better understood and appreciated from the following detailed description of the embodiments thereof, selected for purposes of illustration and shown in the accompanying Figs and Example. It should therefore be understood that the particular embodiments illustrating the present invention are exemplary only and not to be regarded as limitations of the present invention.